Forecasting quakes means understanding processes that is happening below surface. San Andreas Fault is the most active and dangerous fault in earth. It is a 1200km long massive fault through California in united state. It is the tectonic boundary between North American plate and pacific plate. Every year many quakes are produced by San Andreas Fault. Most of them are small. But some grow into catastrophic scale. As no one can tell when the friction of two tectonic plates will be released, it is currently impossible to forecasst earthquake.